In the hope that it may save others a bad experience, here's what
happened recently to me with these vendors.

I placed an order with thebenzbin.com in July for a muffler and header
pipe and it was my worst internet buying experience ever.   No email
confirmation, took almost 2 months to ship the muffler, which came
unboxed and all dented and mangled.  Oh, and they charged my credit
card at the time the order was placed.   Despite repeated phone calls
over 2 months, I could never get an answer as to the status of the
header pipe.  Every time I called it was starting all over with
someone new.    No returned phone calls and no response to emails
either.   Finally, calling them again in early Sept, they told me
"Sir, the header pipe order was cancelled last week and your money
refunded."   And how was I supposed to know this?

So, then I place the order for the header pipe with Carstuff.com over
the phone.  The guy I spoke with looks up the part, assures me they
have it and can supply it.   I even told him my experience with
TheBenzBin and asked if he ever heard of them.  Answer:  no

Well, a few days later, I go log back on to thebenzbin website to
check my return status and guess what?    Incredibilly, it now shows a
new order, which is the one I placed over the phone with Carstuff.
So, clearly these 2 companies are linked.

So, now I get on the phone and call up Carstuff and read them the riot
act.   Telling them I just went through 2 months of screwing around
with thebenzbin and now it looks like I've placed the same order all
over again with the same company for a part they can't supply.
Carstuff admitted they they did in fact have a business relationship
with thebenzbin and a shared order system.  Exactlyt what the
connection is was vague.   He assures me the muffler has already
shipped and the header pipe is sitting in the warehouse right next to
his building.   I ask for tracking # for the muffler and he says he
will email it and also one for the header pipe.   No email ever
comes.    Both of these turn out to be lies.   The muffler did not
ship until days later.  They never had the header pipe and finally
refunded my money.

The guy at Carstuff told me to email pics for the RMA of the muffler
from thebenzbin to photos@usautoparts.com.   So, since the guy at
carstuff can process RMA's for parts bought at thebenzbin, clearly
carstuff and thebenzbin are linked.  Plus, now I have what appears to
be a third companies internet address, usautoparts.com.

If you go to the BBB for southern California and check out
usautoparts.com, they have an F rating.

http://www.labbb.org/BBBWeb/Forms/Business/CompanyReportPage_Expository.aspx?Com
panyID=100006368

I'd stay away from all the above companies.

I finally got the header pipe from Rusty's MB parts.   He told me
right away that the header pipe was now only available direct from
MB.  And he got it for me quickly at a good price.